准噶尔盆地西南缘构造模式、演化及其油气

通过地震勘探、钻井、地面地质资料综合分析,列出了6点依据,认为,盆地南缘西部构造特征是3个深浅层次的北凸孤形滑脱体。它们分别为燕山和喜山运动由南向北的侧向挤压造就而成。圈闭的含油气性,总的说来西段较东段好。     

龙门山南西段一个不成峰的飞来峰构造

大偏崖飞来峰是一个产于河谷中的飞来峰,其中产Pseudo fusulina kraffli。属海相早二叠世早期(隆林期)的生物,与上扬子地台梁山期的海陆交互相共处在一地。据此化石和参考龙门山相近地区飞来峰的(竹蜓)化石及其他化石组合,推断飞来峰是来自川西-藏东地区。根据大偏崖飞来峰的产出形态、构造地质特征与地貌的关系,确定龙门山前山带的上古生界是一个不生根的大飞来峰,其生物化石组合与近邻的龙门山后山及上扬子地台不相同,与川西-藏东-带确可对比。据此推断上扬子地台在印支晚期发生过逆掩推覆构造运动,其后在燕山—喜马拉雅期,上扬子地台驮负着龙门山向北东方向作左旋运动,同时向北西俯冲形成龙门山。     

新疆东部古地磁研究

沿富蕴—二台—苏古泉—七角井—沙泉子—柳园—阿克塞对奥陶系—上第三系进行古地磁研究,主要获得以下成果:(1)建立了北准噶尔地片和东准噶尔地片极移曲线,认为准噶尔洋形成于泥盆纪—石炭纪,在二叠纪闭合。这两个地片在早古生代是一个统一的构造单元,位于30°S左右,泥盆纪拉开距离达1000km,其北边的地片位移于20°—30°N左右,早古生代晚期到晚古生代早期是地块快速北向移动时期;(2)获得了七角井、沙泉子和柳园地区石炭、二叠纪古地磁极位置及古纬度,其中的柳园、沙泉子地区极点位置明显与准噶尔不一致,而与哈萨克斯坦西天山(伊犁地块)、塔城地块、吐哈地块、鄂尔多斯地块及华北地块等古地磁极接近,说明这些地块在晚古生代已处于南、北大陆之间,成为独立的中间地体;(3)通过新疆东部和北部晚古生代到早第三纪古地磁研究,进一步证明了东亚地区从中生代开始南向移动的存在;(4)准噶尔地块在晚古生代处于30°—35°N的古纬度区,准噶尔洋主要为近EW向拉开,如果存在SN向移动,其相对移动距离也不会超过1500km。(b)从晚古生代以来的北方大陆块体构造演化模式来看,准噶尔地块大致遵循了北方大陆块体统一的构造演化规律,说明准噶尔地块是北方大陆的组成部分。     

北祁连走廊南山加里东俯冲杂岩增生地体及其动力学

北祁连走廊南山加里东火山岛弧带前缘为弧前俯冲杂岩增生地体。它由多重的增生火山岛弧、复理石增生楔、高压变质滑脱带及蛇绿岩残片组成，为早古生代古祁连洋壳自ＳＷ往ＮＥ俯冲于阿拉善地块之下的结果。俯冲过程的高压变质阶段经历了中温高压的初期、降温增压的主期而进入降压增温的驰后期。提出了４５０－５００Ｍａ期间，中祁连地块向北俯冲、阿拉善地块向南增生的海沟后退的俯冲动力学模式。     

A kinematics-uplift model for the HimalayanTibetan region

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滇西南昌宁-孟连带南段群沉积特征及其构造古地理意义──兼论临沧地体的性质

南段群位于滇西南昌宁－孟连带东区，为一套厚度巨大的砂岩与泥板岩互层的类复理石沉积类型，是由非正常滑塌浊流、正常浊流和碎屑流沉积作用形成的特殊沉积物，其沉积构造背景为被动大陆边缘的深水陆坡环境，物源区为临沧地体。临沧地体在早石炭世至早二叠世具有亲冈瓦纳性质，晚二叠世前增生到思茅地块西缘。     

Late Palaeozoic arc flank and fore‐arc basin sequence of the New England fold belt in the stanage bay region,central Queensland

Devonian and Carboniferous (Yarrol terrane) rocks, Early Permian strata, and Permian‐(?)Triassic plutons outcrop in the Stanage Bay region of the northern New England Fold Belt. The Early‐(?)Middle Devonian Mt Holly Formation consists mainly of coarse volcaniclastic rocks of intermediate‐silicic provenance, and mafic, intermediate and silicic volcanics. Limestone is abundant in the Duke Island, along with a significant component of quartz sandstone on Hunter Island. Most Carboniferous rocks can be placed in two units, the late Tournaisian‐Namurian Campwyn Volcanics, composed of coarse volcaniclastic sedimentary rocks, silicic ash flow tuff and widespread oolitic limestone, and the conformably overlying Neerkol Formation dominated by volcaniclastic sandstone and siltstone with uncommon pebble conglomerate and scattered silicic ash fall tuff. Strata of uncertain stratigraphic affinity are mapped as ‘undifferentiated Carboniferous’. The Early Permian Youlambie Conglomerate unconformably overlies Carboniferous rocks. It consists of mudstone, sandstone and conglomerate, the last containing clasts of Carboniferous sedimentary rocks, diverse volcanics and rare granitic rocks. Intrusive bodies include the altered and variably strained Tynemouth Diorite of possible Devonian age, and a quartz monzonite mass of likely Late Permian or Triassic age.

The rocks of the Yarrol terrane accumulated in shallow (Mt Holly, Campwyn) and deeper (Neerkol) marine conditions proximal to an active magmatic arc which was probably of continental margin type. The Youlambie Conglomerate was deposited unconformably above the Yarrol terrane in a rift basin. Late Permian regional deformation, which involved east‐west horizontal shortening achieved by folding, cleavage formation and east‐over‐west thrusting, increases in intensity towards the east.     

The Phuket-Slate Belt terrane: tectonic evolution and strike-slip emplacement of a major terrane on the Sundaland margin of Thailand and Myanmar

The Phuket-Slate Belt terrane can be traced for 1700 km from Phuket to Mandalay, and has a distinct stratigraphy and tectonic history. It is characterized by a very thick Carboniferous-Lower Permian succession which includes diamictites interpreted as glacio-marine rift-infill deposited when the Sibumasu block separated from Gondwana. It was emplaced in the Late Cretaceous-Palaeogene by dextral strike-slip movement on a fault system which includes the Khlong Marui and Panlaung Faults. Southwards the Khlong Marui bounding-fault and its close associate, the Ranong Fault, are postulated to extend to Sumatra where they align with the restored proto-Indian Ocean location of the India–Australia transform at the time that both were undergoing dextral displacement and Greater India was moving toward its collision with Eurasia. It is suggested that emplacement of the Phuket-Slate Belt terrane was the result of its coupling with the north-going India plate, resulting in up to about 450 km of dextral shift on the terrane's bounding fault system. Post-emplacement sinistral movement on the cross-cutting Mae Ping and Three Pagodas Faults offset the terrane boundary resulting in its present outline.     

Architecture of a Palaeoproterozoic Rift System: Evidence from the Fiery Creek Dome region,Mt Isa terrane

The Mt Isa Rift Event is a Palaeoproterozoic intracontinental extension event that defines the beginning of sedimentation into the Isa Superbasin in the Western Fold Belt, Mt Isa terrane. In the mildly deformed Fiery Creek Dome region, on the northwest flanks of the Mt Isa Rift, elements of the Mt Isa Rift Event rift architecture are preserved without being intensely overprinted by later deformation. In this region two discrete generations of northwest‐dipping normal faults have been identified. Early generation normal faults were active during the deposition of fluvial and immature conglomerate and sandstone of the Bigie Formation. Renewed rifting and the development of late‐generation normal faults occurred during deposition of shallow‐marine sandstone and siltstone of the lower Gunpowder Creek Formation. Differential uplift between tilt blocks formed an array of spatially and temporally discontinuous synrift unconformities on the crests of uplifted tilt blocks. Applying the domino model yields ～28% crustal extension for the entire Mt Isa Rift Event. Northwest‐striking transverse faults facilitated differential displacement along normal faults and formed boundaries to normal fault segments, creating smaller depositional compartments along half‐graben axes. Three large domes were formed during laccolith emplacement. These domes produced palaeogeographical highs that divided the region into sub‐basins and were a source for the coarse fluvial synrift sequences deposited during the early Mt Isa Rift Event. The basin architecture in the Fiery Creek Dome region is consistent with northwest‐southeast‐directed extension.     

Growth and deformation of porphyroblasts in the Foothills terrane, central Sierra Nevada, California: negotiating a microstructural minefield

Abstract The main porphyroblastic minerals in schists and phyllites of the Foothills terrane, Western Metamorphic Belt, central Sierra Nevada, California, are cordierite and andalusite (mostly chiastolite). Less commonly, biotite, muscovite, chlorite, garnet or staurolite are also present as porphyroblasts. The variety of porphyroblast and matrix microstructures in these rocks makes them suitable for testing three modern hypotheses on growth and deformation of porphyroblasts: (1) porphyroblast growth is always syndeformational; (2) porphyroblasts nucleate only in low-strain, largely coaxially deformed, quartz-rich (Q) domains of a crenulation foliation and are dissolved in active high-strain, non-coaxially deformed, mica-rich (M) domains, the spacing between which limits the size of the porphyroblasts; and (3) porphyroblasts generally do not rotate, with respect to geographical coordinates, during deformation, provided they do not deform internally, so that they may be used as reliable indicators of the orientation of former regional structural surfaces, even on the scale of orogenic belts. Some porphyroblast–matrix relationships in the Foothills terrane are inconsistent with hypotheses 1 and 2, and others are equivocal. For example, in many rocks it cannot be determined whether the porphyroblasts grew where the strain had already been partitioned into M and Q domains, whether the porphyroblasts caused this partitioning, or both. Although most porphyroblasts appear to be syndeformational, as predicted by hypothesis 1, observations that do not support the general application of hypotheses 1 and 2 to rocks of the Foothills terrane include: (a) lack of residual crenulations in many strain-shadows and alternative explanations where they are present; (b) absence of porphyroblasts smaller than the distance between nearest mica-rich domains; (c) nucleation of crenulations on existing porphyroblasts, rather than nucleation of porphyroblasts between existing crenulations; (d) presence of micaceous ‘arcs’in an undifferentiated matrix against some porphyroblasts, suggesting static growth; (e) absence of crenulations in porphyroblastic rocks showing sedimentary bedding; and (f) porphyroblasts with very small, random inclusions, which are probably pre-deformational. Similarly, porphyroblasts that have overgrown sets of crenulations and porphyroblasts with micaceous ‘arcs’are probably post-deformational, at least on the scale of a large thin section and probably over much larger areas, judging from mesoscopic structural evidence. Some porphyroblasts in rocks of the Foothills terrane do not appear to have rotated, with respect to geographical coordinates, during matrix deformation, in accordance with hypothesis 3, at least on the scale of a large thin section. However, other porphyroblasts evidently have rotated. In some instances, this appears to be due to mutual interference, but many apparently rotational porphyroblasts are too far apart to have interfered with each other, which indicates that the rotation was associated with deformation of the matrix. The occurrence of planar bedding surfaces adjacent to porphyroblasts about which bedding and/or foliation surfaces are folded suggests rotation of the porphyroblasts during non-coaxial flow parallel to bedding, rather than crenulation of the matrix foliation around static porphyroblasts. It appears that porphyroblasts may rotate during deformation if the matrix is relatively homogeneous, so that the strain is effectively non-coaxial. This may occur after homogenization of a matrix in response to the strongest degree of crenulation folding, whereas the same porphyroblasts may have been inhibited from rotating previously, when strain accumulation was partitioned in the matrix.